Conventional gasoline vehicles run mainly by driving a gasoline engine, and due to an increase in environmental pollution from the gasoline vehicles, electric vehicles in which an engine is driven by motor operation based on electricity have been developed.
Such gasoline vehicles emit a great deal of exhaust gases, thus increasing an environmental pollution. On the other hand, the electric vehicles may prevent environmental pollution, however since the electric vehicles run by batteries, they cannot drive for a long period of time.
As a solution to the problems of the gasoline vehicles and electric vehicles, hybrid electric vehicles having complex functions of both gasoline vehicles and electric vehicles have been introduced.
A hybrid electric vehicle is equipped with a general gasoline engine driving function and an electric motor driving function, and thus, the hybrid electric vehicle may be driven as a general gasoline vehicle or as an electric vehicle as necessary.
Since a hybrid electric vehicle includes components different from those of an existing gasoline vehicle or electric vehicle such as an engine, an alternator, a battery, a motor, and the like, various vehicle starting methods such as ON/OFF control of an engine alternator, and the like, according to battery power conditions are required when a vehicle is running.
When a hybrid electric vehicle is discharged, generally, a household power source is connected to a jump port provided in the hybrid electric vehicle and an engine starts using power processed through an AC-DC converter, a driving battery, a DC-DC converter, and a generator.
Since a lithium ion battery has been used in the hybrid electric vehicle, a jump-starting method using an external power source has been continuously used when the hybrid electric vehicle is over-discharged. However, in this case, a relay is frequently fused or a lithium ion battery is damaged in jump-starting.